Method of making an electrochemical cell having a safety vent closure

ABSTRACT

A safety blow-out vent closure for galvanic cells, such as nonaqueous oxyhalide cells, which comprises the employment of a conductive tubular member secured to the cell&#39;s housing and surrounding a vent orifice in the cell&#39;s housing and wherein a deformable member is force-fitted in said vent orifice and adapted to at least partially be ejected from the vent orifice upon the build up of a predetermined internal gas pressure within the cell. The invention is also directed to a method for assembling an electrochemical cell with the above-described safety vent closure.

This is a division of our prior U.S. application Ser. No. 190,990,filing date Sept. 26, 1980, now U.S. Pat. No. 4,329,405.

FIELD OF THE INVENTION

This invention relates to a safety, non-resealable vent closure forgalvanic cells, such as nonaqueous cells, which comprises the employmentof a conductive tubular member disposed about and secured over a ventorifice in the cell's housing and wherein a deformable member isforce-fitted within the vent orifice thereby providing a normallyfluid-tight seal at said vent orifice. The invention also relates to amethod of producing the safety vent closure of this invention.

BACKGROUND OF THE INVENTION

Galvanic cells may generate large quantities of gas under certainconditions during use. Since many such cells are required to be tightlysealed in order to prevent loss of electrolyte by leakage, high internalgas pressures may develop. Such pressures may cause leakage, bulging orpossible rupture of the cell's container under abusive conditions if notproperly vented.

In the past, several different types of resealable pressure relief ventvalves have been used for releasing high internal gas pressures frominside a sealed galvanic cell. One type of valve that has been commonlyused consists basically of a valve member such as a flat rubber gasketwhich is biased into sealing position over a vent orifice by means of aresilient member such as a helical spring. The resilient member orspring is designed to yield at a certain predetermined internal gaspressure so as to momentarily break the seal and allow the gas to escapethrough the vent orifice.

In U.S. Pat. No. 3,664,878 to Amthor issued on May 23, 1972, aresealable vent is disclosed which comprises a resilient deformable ballof elastomeric material positioned to overlie a vent orifice providedwithin the cell's container. A retainer means is positioned over theresilient ball for maintaining the ball in place over the vent orificeand in contact with a valve seat provided around the peripheral edgeportions of the vent orifice and for compressing and deforming theresilient ball into a flattened configuration forming a normallyfluid-tight seal between the flattened ball and the valve seat. Theresilient ball is capable of undergoing further temporary deformationupon the build up of a predetermined high internal gas pressure insidethe container so as to momentarily break the seal and allow gas toescape through the vent orifice.

However, with the continuing development of portable electricallypowered devices such as tape recorders and playback machines, radiotransmitters and receivers, and the like, a new type of reliable, longservice life cells or batteries has been developed. These newlydeveloped electrochemical cell systems provide a long service life byutilizing highly reactive anode materials such as lithium, sodium andthe like, in conjunction with high energy density nonaqueous liquidcathode materials and a suitable salt.

It has recently been disclosed in the literature that certain materialsare capable of acting both as an electrolyte carrier, i.e., as solventfor the electrolyte salt, and as the active cathode for a nonaqueouselectrochemical cell. U.S. Pat. No. 4,400,453 issued Aug. 23, 1983discloses a nonaqueous electrochemical cell comprising an anode, acathode collector and a cathode-electrolyte, said cathode-electrolytecomprising a solution of an ionically conductive solute dissolved in anactive cathode depolarizer wherein said active cathode depolarizercomprises a liquid oxyhalide of an element of Group V or Group VI of thePeriodic Table. The "Periodic Table" is the Periodic Table of Elementsas set forth on the inside back cover of the Handbook of Chemistry andPhysics, 48th Edition, The Chemical Rubber Co., Cleveland, Ohio,1967-1968. For example, such nonaqueous cathode materials would includesulfuryl chloride, thionyl chloride, phosphorus oxychloride, thionylbromide, chromyl chloride, vanadyl tribromide and selenium oxychloride.

Another class of liquid cathode materials would be the halides of anelement of Group IV to Group VI of the Periodic Table. For example, suchnonaqueous cathode material would include monochloride, sulfurmonobromide, selenium tetrafluoride, selenium monobromide,thiophosphoryl chloride, thiophosphoryl bromide, vanadium pentafluoride,lead tetrachloride, titanium tetrachloride, disulfur decafluoride, tinbromide trichloride, tin dibromide dichloride and tin tribromidechloride.

It has been found that when employing high energy density liquid cathodematerials in nonaqueous cell systems, the cells exhibit higher voltagesthan cells employing conventional aqueous systems which results in fewercell units being required to operate a particular battery-powdereddevice. In addition, many of the oxyhalide and halide nonaqueous cellsdisplay relatively flat discharge voltage-versus-time curves. Thus thesecells can be employed to produce batteries that will provide a workingvoltage closer to a designated cut-off voltage than is practicable withsome conventional aqueous systems which generally do not exhibit flatdischarge voltage-versus-time curves.

However, one possible disadvantage in the use of oxyhalide and halideliquid cathode nonaqueous cells is that it may be possible that duringstorage or use, some of the oxyhalide, halide or their reaction productsmay escape from the cell. This escape of liquids and/or gases couldcause damage to the device employing the cell or to the surface of acompartment or shelf where the cell is stored. On the other hand, if theseal of the cell is effectively permanently secured, then it is possiblethat the build up of internal pressure within the cell could cause thecell's container to rupture which may cause property and/or bodilydamage. To prevent rupture of the cell's container from possibleinternal pressure build up caused under abusive conditions, such ascharging and exposure to a high temperature environment, it is necessaryto vent the cell at some predetermined pressure. It has been reportedthat some oxyhalides such as thionyl chloride and sulfuryl chlorideshould be vented at pressures below about 500 psi and preferably betweenabout 150 and 300 psi.

It is, therefore, an important object of this invention to provide asafety non-resealable vent closure for electrochemical cells,specifically oxyhalide cells.

It is another object of this invention to provide a safetynon-resealable vent closure for cylindrical cells employing, forexample, oxyhalides as the active cathodic material.

It is another object of this invention to provide a safetynon-resealable vent closure for nonaqueous cells that is inexpensive tomanufacture and easy to assemble.

It is another object of the present invention to provide a method forassembling the solid components of the cell in a container followed byclosing the container with a cover and then adding the liquid componentsof the cell prior to assembling the safety vent closure of thisinvention onto the cell's housing.

The foregoing and additional objects will become fully apparent from thefollowing description and the accompanying drawings.

SUMMARY OF THE INVENTION

The invention relates to an electrochemical cell in which the activecomponents of the cell are assembled within a housing comprising acontainer sealed at its open end by a cover, and having at least onevent orifice, the improvement being a safety vent closure comprising aconductive tubular member secured to the housing and surrounding thevent orifice, a deformable member force-fitted within the vent orificethereby providing a normally fluid-tight seal over said vent orifice;and wherein said deformed member is adapted to be at least partiallyexpelled from the vent orifice upon a build up of a predeterminedinternal gas pressure inside the cell thereby providing a permanent ventpassage.

Preferably, a layer of a sealant material such as asphalt or wax couldbe disposed within the tubular member over the deformable member and thearea of the housing defining the vent orifice surrounded by the tubularmember. The advantage of the sealant material is that it will providemaximum leakage resistance as well as further increase reliability tovent after a predesignated pressure builds up. Suitable sealingmaterials could include halocarbon wax which is a saturatedlow-molecular weight polymer of chlorotrifluoroethylene having thegeneral formula: --(CH₂ --CFCl)_(n) --, asphalt, epoxy or any materialswhich are resistant to moisture, have reasonable adhesion to metal andcan be applied easily. Preferably the material should be applied inliquid form and then set to a solid.

The invention also relates to a method for assembling an electrochemicalcell having a safety vent closure which comprises the steps:

(a) placing the solid components of a cell within the container of acell's housing, said housing comprising the container having secured atits open end a cover and said housing having at least one vent orifice;

(b) feeding the liquid component of the cell through the vent orificeinto the housing; and

(c) force-fitting a deformable member into the vent orifice therebyproviding a fluid-tight seal over said vent orifice.

In the above-described method step (d) could be added as follows:

(d) placing a layer of a sealant over the deformable member and the areaof the housing defining the vent orifice.

Preferably, in the above-described method the steps (a) and (d) could beperformed as follows:

(a) placing the solid components of a cell within the container of acell's housing, said housing comprising the container having secured atits open end a cover and wherein at least one tubular member is securedto said housing and surrounds at least one vent orifice; and

(d) placing a layer of a sealant within said tubular member over thedeformable member and the area of the housing defining the vent orificeand surrounded by the tubular member.

As used herein, the deformable material has to be made of a material orcoated with a material that is chemically resistant to the cell'scomponents, particularly the cell's liquid components, and have ahardness greater than 100 on the Shore A scale*. The deformable materialshall also have a modulus of elasticity (Young's Modulus) between about0.01×10⁶ psi and about 28×10⁶ psi and preferably between about 0.03×10⁶and 20×10⁶ psi. For nonaqueous oxyhalide cell systems, the deformablematerial can be selected from the group consisting ofpolytetrafluoroethylene, fluorinated ethylene propylene polymer,perfluoroalkoxyethylene polymer, ethylene tetrafluoroethylene polymerand the like. When the deformable material is to be coated with achemically inert material, the said deformable material can be selectedfrom the group consisting of nylon, lead, hard rubber and the like.Other suitable materials for use in this invention but not suitable forsome of the oxyhalide cell systems are nylon, polypropylene,polycarbonate, acrylic polymers and the like.

As used herein, the tubular member can be cylindrical, square,rectangular or have any polygonal shaped cross section. In the preferredembodiment, the cell will be a cylindrical cell in which the ventorifice is disposed in the cell's cover and wherein the conductivetubular member, which serves as an electrical terminal for the cell,will be a cylindrical member having an outwardly disposed flange at oneend which is adapted for securing to the cell's cover. The tubularmember is ideally suited as an element to which conductive strips can bewelded to serve as external leads. Preferably, the deformable membershould have a smooth spherical configuration and the wall defining thevent orifice should be substantially smooth.

The safety vent closure of this invention can be made to vent at anypredetermined pressure build up within the cell by regulating the sizeof the vent opening with respect to the size of the deformable member,the material of which the deformable member is made, the degree ofdeformation required of the deformable member upon its insertion intothe vent orifice, and the shapes of the vent opening and the deformablemember. Using the teachings of this invention, the deformable membercould be inserted rapidly into the orifice with a minimum of force toattain a reliable and predictable safety vent closure. The use of acontrolled height dead-stop ram to insert the deformable member would bemost desirable for automatic assembly operations.

It has been found that for 0.475 inch diameter cells an ideal safetyvent closure can be had using a cover thickness of 0.05 inch, a circularvent orifice of 0.086 inch diameter, a deformable ball ofpolytetrafluoroethylene measuring 0.094 inch in diameter and aconventional ram employing a push-in force of 25 pounds.

A preferred version of the safety vent closure of this inventionutilizes a polytetrafluoroethylene ball with a halocarbon wax oversealin which the ball is compressed 10 to 15 percent upon insertion into avent opening in a lithium/oxyhalide cell. Once inserted, the ball willassume a substantially spherical configuration. Cells of this type weretested and found to exhibit no leakage at 25° C. and 100% relativehumidity over long periods of time. In the abuse testing of these typecells wherein the cells were charged at up to 2 amperes and on testingof the cells in an incinerator at temperatures as high as 865° C., allthe cells vented properly without any container rupture. Thus thesubject invention is ideally suited for lithium/oxyhalide cell systems,specifically those employing sulfuryl chloride and/or thionyl chloride.

The safety non-resealable vent closure of this invention preferably canbe employed with all size cylindrical cells and is ideally suited forliquid cathode cell systems employing, for example, a liquid oxyhalide.In addition to providing an excellent and effective safety ventingmeans, the invention also permits the initial assembling of the solidcomponents of a cell within a container that can be closed in aconventional manner before adding the cell's liquid component. When thecell's liquid component is an oxyhalide-based liquid cathode, such asthionyl chloride or sulfuryl chloride, then these corrosive liquids canbe injected into the cell's housing through the small vent orifice,e.g., by vacuum filling, after the cell cover is secured to thecontainer. This will effectively eliminate the corrosion of crimpingequipment used to close the cell as well as eliminating contamination atthe interfaces of the container-gasket and gasket-cover of the cell bythe oxyhalide.

A cell for use in this invention can be the split internal anode/outercathode collector construction as described in U.S. Pat. No. 4,032,696or the split internal cathode collector construction as described inU.S. Pat. No. 4,048,389, said U.S. Pat. Nos. 4,032,696 and 4,048,389being incorporated herein by reference.

Suitable nonaqueous liquid cathode materials for use in cells of thisinvention could be one or more of the liquid oxyhalides of an element ofGroup V or Group VI of the Periodic Table and/or one or more of thehalides of an element of Group IV or Group VI of the Periodic Table,said Periodic Table being the Periodic Table of Elements as set forth onthe inside back cover of the Handbook of Chemistry and Physics, 48thEdition, The Chemical Rubber Co., Cleveland, Ohio, 1967-1968. Forexample, such nonaqueous cathode materials would include sulfurylchloride, thionyl chloride, phosphorus oxychloride, thionyl bromide,chromyl chloride, vanadyl tribromide, selenium oxychloride, sulfurmonochloride, sulfur monobromide, selenium tetrafluoride, seleniummonobromide, thiophosphoryl chloride, thiophosphoryl bromide, vanadiumpentafluoride, lead tetrachloride, titanium tetrachloride, disulfurdecafluoride, tin bromide trichloride, tin dibromide dichloride and tintribromide chloride. Another suitable cathode material would be liquidsulfur dioxide.

Anodes suitable for use in nonaqueous liquid cathode cell systems can begenerally consumable metals and include the alkali metals, alkalineearth metals and alloys of alkali metals or alkaline earth metals witheach other and other metals. The term "alloy" as used herein is intendedto include mixtures; solid solutions such as lithium-magnesium; andintermetallic compounds such as lithium monoaluminide. The preferredanode materials are the alkali metals and particularly lithium, sodiumand potassium. When using lithium anodes the anode may be coated with avinyl resin as disclosed in U.S. Pat. No. 3,993,501, said patentincorporated herein by reference.

The cathode collector for use in liquid cathode cell systems has to beelectronically conductive so as to permit external electrical contact tobe made with the active cathode material and also provide extended areareaction sites for the cathodic electrochemical process of the cell.Materials suitable for use as a cathode collector are carbon materialsand metals such as nickel, with acetylene black being preferable. Inaddition, the cathode collector when made of a particulate materialshould be capable of being molded directly within a can or capable ofbeing molded into various size discrete bodies that can be handledwithout cracking or breaking. To impart a cohesive characteristic tosome types of cathode collectors, such as carbonaceous cathodecollectors, a suitable binder material, with or without plasticizers andwith or without stabilizers, can be added to the cathode collectormaterials. Suitable binder materials for this purpose may include vinylpolymers, polyethylene, polypropylene, polyacrylics, polystyrene and thelike. For example, polytetrafluoroethylene would be the preferred binderfor cathode collectors for use with liquid oxyhalide cathodes. Thebinder, if required, should be added in an amount between about 5% andabout 30% by weight of the molded cathode collector since an amount lessthan 5% would not provide sufficient strength to the molded body whilean amount larger than 30% would wetproof the surface of the carbonand/or reduce the available surface of the carbon, thereby reducing theactivation site areas required for the cathodic electrochemical processof the cell. Preferably, the binder should be between 10% and 25% byweight of the cathode collector. Of importance in selecting thematerials for the cathode collector is to select materials that will bechemically stable in the cell system in which they are to be used.

A solute for use in liquid cathode cell systems may be a simple ordouble salt which will produce an ionically conductive solution whendissolved in a suitable solvent. Preferred solutes for nonaqueoussystems are complexes of inorganic or organic Lewis acids and inorganicionizable salts. The only requirements for utility are that the salt,whether simple or complex, be compatible with the solvent being employedand that it yield a solution which is ionically conductive. According tothe Lewis or electronic concept of acids and bases, many substanceswhich contain no active hydrogen can act as acids or acceptors ofelectron doublets. The basic concept is set forth in the chemicalliterature (Journal of the Franklin Institute, Vol. 226, July/December,1938, pages 293-313 by G. N. Lewis).

A suggested reaction mechanism for the manner in which these complexesfunction in a solvent is described in detail in U.S. Pat. No. 3,542,602wherein it is suggested that the complex or double salt formed betweenthe Lewis acid and the ionizable salt yields an entity which is morestable than either of the components alone.

Typical Lewis acids suitable for use in conjunction with liquidoxyhalide cathodes include aluminum fluoride, aluminum bromide, aluminumchloride, antimony pentachloride, zirconium tetrachloride, phosphoruspentachloride, boron fluoride, boron chloride and boron bromide.

Ionizable salts useful in combination with the Lewis acids includelithium fluoride, lithium chloride, lithium bromide, lithium sulfide,sodium fluoride, sodium chloride, sodium bromide, potassium fluoride,potassium chloride and potassium bromide.

It will be obvious to those skilled in the art that the double saltsformed by a Lewis acid and an ionizable salt may be used as such or theindividual components may be added to the solvent separately to form thesalt or the resulting ions in situ. One such double salt, for example,is that formed by the combination of aluminum chloride and lithiumchloride to yield lithium aluminum tetrachloride.

If desired, and specifically for the halides, a cosolvent should beadded to the liquid active reducible cathode and solute solution toalter the dielectric constant, viscosity or solvent properties of thesolution to achieve better conductivity. Some examples of suitablecosolvents are nitrobenzene, tetrahydrofuran, 1,3-dioxolane,3-methyl-2-oxazolidone, propylene carbonate, γ-butyrolactone, sulfolane,ethylene glycol sulfite, dimethyl sulfite, benzoyl chloride,dimethoxyethane, dimethyl isoxazole, diethyl carbonate, sulfur dioxideand the like.

Suitable separators for use with liquid cathodes in nonaqueous cellssuitable for use in nonaqueous liquid cathode cell systems are thenonwoven glass separators, preferably those separators that incorporatelong glass fibers along with the short glass fibers since such acombination increases the tear strength of the separators thereby makingthem easier to handle.

The container of the cell could be made of stainless steel, iron,nickel, plastic, coated metals or some other suitable material.

Some preferred combinations of nonaqueous cathode materials and anodeswould be as follows:

(1) sulfuryl chloride/Li or Na;

(2) thionyl chloride/Li or Na;

(3) phosphorus oxychloride/Li or Na;

(4) sulfur monochloride/Li or Na;

(5) sulfur monobromide/Li or Na;

(6) selenium tetrafluoride/Li or Na.

Preferably, the cells for use in this invention would be liquidoxyhalide cells using sulfuryl chloride, thionyl chloride or mixturesthereof with a lithium anode.

It is to be understood that the safety vent closure of this inventioncould be used in other cell systems such as, for example, Leclanche drycells, zinc chloride cells, lithium-MnO₂ cells, lithium-iron sulfidecells, alkaline-MnO₂ cells, nickel-cadmium cells, and lead-acid cells.

The present invention will become more apparent from the followingdescription thereof when considered together with the accompanyingdrawing which is set forth as being exemplary of embodiments of thepresent invention and is not intended in any way to be limitativethereof and wherein.

FIG. 1 is a vertical cross sectional view of an electrochemical cellhaving its solid components fully assembled within a housing and beingready for receiving the liquid component of the cell.

FIG. 2 is an enlarged horizontal cross sectional view taken along line2--2 of FIG. 1.

FIG. 3 is a partial vertical cross sectional view of the cell of FIG. 1after the addition of the liquid component and just prior to insertingthe deformable ball into the orifice in the cell's cover.

FIG. 4 is a partial vertical cross sectional view of the cell of FIG. 3after the deformable ball is force fitted into the vent orifice in thecell's cover.

FIG. 5 is a partial vertical cross sectional view of a fully assembledcell.

Referring in detail to FIG. 1, there is shown a cross sectional view ofa cylindrical cell comprising a cylindrical container 2 having disposedtherein a cathode collector shell 4 in contact with the inner upstandingcircumference of the container 2 thereby adapting the container as thecathodic or positive terminal for the cell. Disposed within and incontact with the inner circumference of cathode collector 4 is aseparator liner 6 with its bottom separator or disc 10. If desired, thecathode collector material could be extruded within the container 2,rolled with the container material or composed of one or more segmentsto form a cylindrical tube and then placed in the can.

A two member anode 12 is shown in FIGS. 1 and 2 comprising a first halfcylindrical annular member 14 having flat end faces 16 and 18 and asecond half cylindrical annular member 20 having flat end faces 22 and24. When the flat end faces of each cylindrical half member are arrangedin an opposing fashion as shown in FIGS. 1 and 2, an axial cavity 26 isdefined between the cylindrical half annular members 14 and 20.

If desired, arcuate type backing sheets 15 and 17, such as inertelectrically conductive metal screens or grids, could be disposedagainst the inner surface wall of the anode bodies 14 and 20,respectively, to provide uniform current distribution over the anode.This will result in a substantially uniform consumption or utilizationof the anode while also providing a substantially uniform springpressure over the inner wall surface of anode as will be discussedbelow.

An electrically conductive spring strip 28 is appropriately bent into aflattened elliptically shaped member having an extending end 30. Wheninserting the spring strip 28 into a container, the legs 32, 34 of theconductive strip 28 are squeezed together and forced into the axialopening between the two screen backed anode members arranged in acontainer as shown in FIGS. 1 and 2. The inserted conductive springstrip 28 resiliently biases the two anode members 14 and 20 via backingscreens 15 and 17 so as to provide a substantially uniform andcontinuous pressure contact over the inner wall of the anode members.The extended end 30 of spring strip 28 is shown projected above thesurface of anode members 14 and 20. An insulating gasket 36 has acentral opening 38 through which the projected end 30 of the springstrip 28 passes, whereupon the end 30 is then welded to a cover 40thereby adapting the cover 40 as the anodic or negative terminal of thecell.

Secured to the cover 40 is a cylindrical cap 42. Specifically, thecylindrical cap comprises a cylindrical segment 41 terminating at oneend with an outwardly oriented flange 44 which is secured to cover 40.

The insulating gasket 36 has a peripheral depending skirt 52 disposedbetween the cover 40 and the upper inner wall of the container 2 forclosing the cell through conventional crimping techniques. As shown inFIG. 1, the cylindrical cap is secured to the cover 40 and the cell isclosed using conventional crimping techniques with all of the solidcomponents of the cell assembled within the container 2. After the cellis assembled with the solid components, a hypodermic needle 54 or thelike is used to inject the liquid component into the assembled cell.Specifically, a cathode-electrolyte comprising a suitable salt dissolvedin an oxyhalide, a halide with a cosolvent or mixtures thereof can bedispensed through the cover vent orifice 25 into cavity 26 using thehypodermic needle 54 whereupon it can penetrate through the separatorand cathode collector of the cell.

As shown in FIG. 3, with the cell's liquid component fed into thecontainer, a polytetrafluoroethylene deformable ball 56 is disposed overopening 25 in cover 40 and then a ram member 58 is used to force ball 56into vent orifice 25 as shown in FIG. 4. After removal of the ram 58, alayer of a sealant 60 is disposed over ball 56 and cover 40 withincylindrical member 42 producing a fully sealed cell employing the safetyvent closure of this invention.

Preferably prior to the adding of the liquid component of the cell, avacuum could be created within the cell whereupon the liquid componentcould then be drawn effectively into the cell and uniformly distributedtherein.

The safety vent closure of this invention will provide a means forventing of rapidly generated high pressure gas built up within a cellthereby preventing the rupture of the cell's container.

The following examples are illustrative of the present invention and arenot intended in any manner to be limitative thereof.

EXAMPLE 1

Several cells were made in accordance with FIGS. 1 to 5 using thefollowing components:

anode of lithium,

cathode collector of polytetrafluoroethylene-bonded acetylene black, and

thionyl chloride containing 1.5 M LiAlCl₄.

Each cell measured 0.475 inch diameter and was 1.63 inches long. Thevent orifice measured 0.109 inch in diameter and was 0.05 inch long. Thepolytetrafluoroethylene ball was 0.125 inch in diameter and wasforce-fitted into the vent orifice as shown in FIG. 4. A layer ofhalocarbon wax (obtained from Halocarbon Industries, New Jersey) wasdeposited over the polytetrafluoroethylene ball and the area definingvent orifice as shown in FIG. 5.

Several of the above-described cells were heated in a direct flame at atemperature up to about 865° C. All of the cells vented withoutrupturing the cells' containers. Contrary to this, cells using theabove-identified components and sealed in a conventional manner wouldgenerally show some container rupture when subjected to the same testconditions.

EXAMPLE 2

Several cells were constructed using the same components as in Example 1and employing the resealable vent closure of this invention. The cellswere charged at 2 amperes and all were observed to vent withoutrupturing of the cells' containers. Contrary to this, cells using theabove-identified components and sealed in a conventional manner wouldgenerally show some container rupture when subjected to the same testconditions.

What is claimed is:
 1. A method for assembling an electrochemical cellhaving a safety vent closure which comprises the steps:(a) providing ametal cell housing comprising a container having an open end, a closedend and an upstanding circumference; (b) inserting a cathode collectorshell into said container, said cathode collector being in contact withthe inner upstanding circumference of the container thereby adapting thecontainer as the positive terminal of the cell; (c) disposing aseparator within and in contact with the inner circumference of thecathode collector shell; (d) inserting a multimember anode comprised ofa first half-cylindrical annular member and a second half-cylindricalannular member, each of said members have an inert electricallyconductive metal screen disposed against their inner surface wall, saidfirst and second cylindrical half annular members being disposed in anopposing fashion such that an axial cavity is formed therebetween; (e)disposing an electrically conductive spring strip into the axial cavitybetween the screen-backed anode members such that said strip resilientlybiases the two anode members via said strip so as to provide asubstantially uniform and continuous pressure contact over the innerwall of the anode members; (f) securing a first metal cover over theopen end of said housing, said first cover having at least one ventorifice; (g) securing a second metal cover to the open end of the cell'shousing and placing said second metal cover over said first metal coverwherein at least one metal tubular member is secured to said secondcover and surrounds the vent orifice defined in said first cover; (h)feeding the liquid cathode/electrolyte of the cell through the ventorifice into the housing; (i) force fitting a deformable member into thevent orifice thereby providing a fluid-tight seal over said ventorifice; and (j) placing a layer of sealant having adhesion to metalwithin said metal tubular member over the deformable member and the areaof the first metal cover defining the vent orifice and surrounded by thetubular member.
 2. The method of claim 1 wherein the liquidcathode/electrolyte added in step (h) comprises at least one liquidoxyhalide selected from the group consisting of thionyl chloride,sulfuryl chloride, phosphorous oxychloride, thionyl bromide, chromylchloride, vanadyl tribromide and selenium oxychloride.
 3. The method ofclaim 2 wherein the solid anode inserted in step (d) is selected fromthe group consisting of lithium, sodium, calcium, potassium andaluminum.